Unit 8 · Segment 3: The Distribution of Earth's Resources · printed p. 294 (PDF p. 330)
States of Matter
Ice eventually turns into water when it is left out, and water boils and seems to disappear when it is heated.
Anchoring phenomenon
Chapters
- 23 The Motion of Particles
How does the motion of particles explain what a solid, a liquid and a gas can do, and what happens to that motion when thermal energy is added or removed?
1 presentation10 worksheets3 labs - 24 Heat, Temperature, and State Changes
When thermal energy is added to or removed from a substance, what happens to how its particles move, to its temperature and to its state?
1 presentation10 worksheets3 labs
Standards in this unit
Unit vocabulary
state of matterThe form a sample takes, solid, liquid or gas, set by how close its particles are and how freely they move.Chapter 23
solidA state in which particles are packed closely in a fixed pattern and can only vibrate around their positions, so the sample keeps its own shape and nearly its own volume.Chapter 23
liquidA state in which particles stay close together but are free to slide past one another, so the sample flows and takes the shape of its container while keeping nearly the same volume.Chapter 23
gasA state in which particles are far apart and move freely in straight lines until they collide, so the sample spreads to fill any container it is given.Chapter 23
temperatureA measure of how fast the particles of a sample are moving on average. A higher temperature means more average kinetic energy per particle.Chapter 23
thermal energyThe total energy of motion of all the particles in a sample. Adding thermal energy usually makes particles move faster, and during a change of state it loosens or separates them instead.Chapter 23
diffusionThe spreading of particles from where they are crowded to where they are fewer, caused only by their own random motion.Chapter 23
melting pointThe temperature at which a pure solid turns into a liquid when it gains thermal energy, at a stated pressure. Freezing happens at the same temperature when energy is removed.Chapter 23
boiling pointThe temperature at which a pure liquid turns into a gas throughout the liquid when it gains thermal energy, at a stated pressure. Lower pressure means a lower boiling point.Chapter 23
pressureThe amount of force pushing on each unit of area. A gas makes pressure when its particles collide with the walls of their container.Chapter 23
state diagramA graph with temperature on one axis and pressure on the other, divided into regions that show where a substance is solid, liquid or gas. Scientists also call it a phase diagram.Chapter 23
sublimationA change straight from solid to gas with no liquid in between, which carbon dioxide does at ordinary air pressure.Chapter 23
temperatureA measure of how energetic a substance's particles are on average: it tracks their average kinetic energy. A thermometer reports this average, not how much energy the whole sample holds.Chapter 24
thermal energyThe sum of the energy of every particle in a sample, from their motion and from how they are arranged against the pulls between them. It depends on how much matter there is, its temperature and its state.Chapter 24
heatEnergy that moves from a warmer object or region to a cooler one because of their temperature difference. In science, heat is energy on the move, not something an object stores.Chapter 24
kinetic energyThe energy an object or particle has because it is moving. The faster a particle of a given mass moves, the more kinetic energy it has.Chapter 24
state changeA change of a substance from one state (solid, liquid or gas) to another. The particles stay the same; only their motion and spacing change. Also called a change of state or phase change.Chapter 24
melting pointThe temperature at which a pure solid turns into a liquid. The liquid freezes at this same temperature. For water it is 0 °C at normal air pressure.Chapter 24
boiling pointThe temperature at which a liquid boils, forming bubbles of its own vapor throughout. It depends on air pressure: water boils at 100 °C at sea level and at a lower temperature high in the mountains.Chapter 24
evaporationThe change from liquid to gas at a liquid's surface, as the most energetic particles escape. It happens at many temperatures, not only at the boiling point, and it cools the liquid left behind.Chapter 24
condensationThe change from gas to liquid, as gas particles lose energy and their attractions hold them together when they collide. It releases energy to the surroundings.Chapter 24
sublimationThe change from solid straight to gas without becoming a liquid first. Dry ice (solid carbon dioxide) sublimes at normal air pressure; snow can slowly sublime on dry, sunny, windy days.Chapter 24
depositionThe change from gas straight to solid without becoming a liquid first, as when water vapor turns into ice crystals on a surface colder than 0 °C. It releases energy.Chapter 24
insulatorA material that slows the transfer of thermal energy. Many insulators, such as foam, wool and bubble wrap, work by trapping still air, which carries energy poorly.Chapter 24